Steve McQueen was cool. So was Paul Newman, Grace Kelly, Kim Novak, Cary Grant, Audrey Hepburn and others from that time.
Nowadays it's really hard to put the cool label on people as there is so much hype that surrounds them, and hype doesn't go with cool. Everything is too immediate, negating the distance necessary to be cool. Off the top of my head someone like Jeff Bridges (the dude) qualifies as cool. I think one would have to look back at this time frame to figure out who qualifies as cool unless you personally know someone who is cool, and then you really wouldn't notice it.
All the best,
Nonoise